Numerous four-way valve assemblies have been developed for controlling liquids and gases, and such assemblies incorporate a wide range of structural and functional features. Such four-way valve assemblies have, for many years, been of substantial size and have often incorporated multiple shiftable valve stems in order to provide for proper control over fluid flow. Modern technology, however, has increasingly demanded that such valve assemblies be made of extremely small size, particularly for use in control circuits. Such assemblies must also permit shifting of the valve with extremely small force without detracting from the desired response time and/or flow.
One of the common problems associated with many known four-way valves, particularly when they use shiftable valves of the poppet type, has been that such assembles often require at least two poppet-type shiftable valve stems in order to provide the desired structural and functional relationships. This increases the structural complexity of the valve assembly, including the size thereof, and also increases the number of seal and wear points.
A further problem associated with known assemblies, particularly those which of are extremely small size so as to be suitable for use in control systems, is the difficulty in maintaining proper tolerances, including axial dimensional relationships between multiple poppets on a single stem and the axial positional relationship of the poppets relative to axially spaced valve seats. The necessary precision of manufacture in order to achieve the necessary tolerances has often been compromised in view of the difficulties in achieving such manufacture, or in view of the impracticality of doing so at reasonable cost.
In an attempt to improve upon the construction of miniaturized four-way poppet valves, the Assignee's U.S. Pat. No. 4 823 842 and the Assignee's application Ser. No. 234,467, now U.S. Pat. No. 4,842,020, disclose single-stem poppet-type four-way valves intended for operation by single or double solenoids. While these latter valves have proven successful for their intended use applications, nevertheless they do not provide the performance characteristics of a high technology precision valve created using conventional manufacturing methods.
Other attempts to provide a precision and miniaturized four-way poppet valve include a valve which employs a housing having five ports including exhaust ports located adjacent opposite ends of the valve stem, and which has no sealed relationship between the valve stem and the adjacent end of the solenoid armature whereby exhaust flow and inlet flow during shifting can enter the coil armature area. This valve also does not permit, within the confines of a one-piece valve housing, isolated exhausts within a single exhaust port. This valve also employs a poppet construction having a radially extending support flange on the valve stem, which support flange on axially opposite sides is provided with separate elastomeric annular inserts which function as poppets for contacting opposed valve seats. This arrangement creates limitations, such as a limited amount of elastomeric material, which are believed to restrict optimum manufacturing and performance requirements of the valve.
Other known valves also possess structural and functional characteristics which are undesirable. For example, many of the known valves have a main valve body provided with five ports including separate widely-spaced exhaust ports for communication with opposite ends of the valve bore, and a separate and often large manifold body must be attached thereto in order to permit individual control over the separate exhausts. Other valves use as many as three poppets on a single stem, or use an undesirable number of seal rings between the stem and housing in order to control flow. All of these features degrade the precision and cost effectiveness associated with the manufacture and operation of such valves.
Accordingly, it is an object of the present invention to provide an improved miniaturized four-way valve employing a single stem having poppets thereon, which valve is direct solenoid actuated.
In the improved valve assembly of this invention, a stem is slidably supported within a bore formed in a one-piece valve body provided solely with four ports, and the stem is hollow to permit the exhaust from two load ports to be directed into an exhaust arrangement, preferably a single exhaust port, located solely at one axial end of the valve body. This exhaust arrangement can desirably be provided with a pair of flow controls to permit individualized control of the exhaust from each load port.
In the improved valve assembly, as aforesaid, the poppets are preferably axially press fit unto the valve stem, particularly on portions of the valve stem which are of slightly different diameters, to facilitate manufacture and assembly of the valve while permitting the individual poppets to be precisely axially positioned relative to one another and relative to the valve seats to achieve high tolerance and precision of operation.
In the improved valve assembly, as aforesaid, the number of sliding seal contacts, such as the number of elastomeric seal rings, is minimized to significantly minimize the breakaway force necessary to permit efficient shifting of the valve stem, and thereby minimize the power requirements of the solenoid while maximizing the responsiveness of the valve assembly.
The valve assembly, as aforesaid, also incorporates an improved poppet arrangement whereby a single elastomeric poppet ring is molded around a radially extending rigid support flange which is mounted on the valve stem, whereby the elastomeric poppet ring integrally defines poppet seal faces on opposite axial sides thereof, and the poppet ring possesses a significant quantity of elastomeric material, whereby the sealing performance of the poppet relative to the opposed valve seats is believed significantly improved.
Other objects and purposes of the present invention will be apparent to persons familiar with valve assemblies of this general type upon reading the following specification and inspecting the accompanying drawings.